Report to fetch Hire Dates in a letter

Summary

Not able to compare among three date in BI Publisher

Content

I have developed a BI Report to extract salary of a person. And after this developed RTF template in BI Publisher. The problem facing is that in the report we have to fetch three dates Original date of Hire, Date_Start from periods of service and another date ATTRIBUTE_DATE1  from per_persons. So now in the report these three dates will be compared like Hire Date contain 01-01-2019, Original Hire Date 01-01-2018, Acquisition Date 01-02-2019, then it will print Original Date of Hire. Now Original Date of Fire or Acquisition Date can be null so null will be not considered in comparison. Suppose